U.S. patent number 7,522,236 [Application Number 11/234,789] was granted by the patent office on 2009-04-21 for cosmetically uniform reflective border area in a transflective display.
This patent grant is currently assigned to Apple Inc.. Invention is credited to Wei Chen, Sherridythe Anne Fraser, Shawn R. Gettemy, John Z. Zhong.
United States Patent |
7,522,236 |
Gettemy , et al. |
April 21, 2009 |
Cosmetically uniform reflective border area in a transflective
display
Abstract
One embodiment of the present invention provides a transflective
display in which a border area adjacent to an active area has a
reflectivity that is substantially the same as the active area when
the display is turned off. This display includes a polarizer layer,
a color filter glass (CFG) layer, a liquid crystal layer, and a
reflector layer. The CFG layer contains color filters in the active
area, while the border area of the CFG layer is designed to have a
reflectivity that is substantially the same as the active area when
the display is turned off.
Inventors: |
Gettemy; Shawn R. (San Jose,
CA), Zhong; John Z. (Cupertino, CA), Fraser; Sherridythe
Anne (Saratoga, CA), Chen; Wei (Palo Alto, CA) |
Assignee: |
Apple Inc. (Cupertino,
CA)
|
Family
ID: |
37893392 |
Appl.
No.: |
11/234,789 |
Filed: |
September 23, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20070070272 A1 |
Mar 29, 2007 |
|
Current U.S.
Class: |
349/114; 349/153;
349/110 |
Current CPC
Class: |
G02F
1/133555 (20130101); G02F 1/133509 (20130101); G02F
1/133388 (20210101) |
Current International
Class: |
G02F
1/1335 (20060101); G02F 1/1333 (20060101); G02F
1/1339 (20060101) |
Field of
Search: |
;349/110,111,114,153 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Qi; Mike
Attorney, Agent or Firm: Park, Vaughan & Fleming LLP
Claims
What is claimed is:
1. A transfective display in which a border area adjacent to an
active area has a reflectivity substantially similar to the active
area when the display is turned off, comprising: a polarizer layer;
a color filter glass (CFG) layer which contains color filters in
the active area; a liquid crystal layer; and a reflector layer
wherein the border area of the CFG layer is fabricated to have a
reflectivity that is substantially the same as the active area,
thereby making the border area visually indistinguishable from the
active area when the display is turned off.
2. The transflective display of claim 1, wherein a given active
pixel in the active area of the CFG layer includes a transmissive
hole for transmitting color via a backlight; and wherein a given
border pixel in the border area of the CFG layer includes a black
mask area whose size and location within the given border pixel are
substantially the same as those of the transmissive hole for a
pixel in the active area.
3. The transflective display of claim 2, wherein the size and
location of the black mask area within the given border pixel is
adjusted to match the reflectivity of a pixel in the active area
when the display is turned off.
4. The transflective display of claim 1, wherein a given pixel in
the CFG layer includes a clear hole that allows ambient light to
reflect directly off of the reflector layer; wherein the clear hole
can be adjusted in size to tune the color point of the given pixel;
and wherein the size of a clear hole in the border area varies from
the size of a clear hole in the active area in order to adjust the
reflectivity in the border area to be substantially the same as in
the active area when the display is turned off.
5. The transflective display of claim 1, wherein the pixel size in
the border area is different from the pixel size in the active
area; and wherein varying the pixel size can adjust the pixel's
light aperture ratio and can thereby change the pixel's
reflectivity.
6. The transflective display of claim 5, wherein the size of pixels
in the border area can vary.
7. The transflective display of claim 1, wherein the cell gap is
the distance between the CFG layer and the reflector layer; and
wherein the cell gap in the border area varies from the cell gap in
the active area; and wherein changing the cell gap in the border
area changes the reflectivity of the border area.
8. The transflective display of claim 1, wherein the surface
roughness of the reflector layer in the border area varies from the
surface roughness of the reflector layer in the active area in
order to modify the reflectivity of the border area.
9. A method for manufacturing a transflective display in which a
border area adjacent to an active area has a reflectivity
substantially similar to the active area when the display is turned
off, the method comprising: forming a polarizing layer; forming a
color filter glass (CFG) layer which contains color filters in the
active area; forming a liquid crystal layer; and forming a
reflector layer; wherein the border area of the CFG layer is
fabricated to have a reflectivity that is substantially the same as
the active area, thereby making the border area visually
indistinguishable from the active area when the display is turned
off.
10. The method of claim 9, wherein a given active pixel in the
active area of the CFG layer includes a transmissive hole for
transmitting color via a backlight; and wherein a given border
pixel in the border area of the CFG layer includes a black mask
area whose size and location within the given border pixel are
substantially the same as those of the transmissive hole for a
pixel in the active area.
11. The method of claim 10, wherein the size and location of the
black mask area within the given border pixel is adjusted to match
the reflectivity of a pixel in the active area when the display is
turned off.
12. A computing device that includes: a computational engine; a
memory-based storage system; and a transflective display used to
present information; wherein the transflective display includes a
border area adjacent to an active area; wherein the border area is
fabricated to have a reflectivity that is substantially the same as
the active area, thereby making the border area visually
indistinguishable from the active area when the display is turned
off.
13. The computing device of claim 12, wherein the transflective
display includes: a polarizer layer; a color filter glass (CFG)
layer which contains color filters in the active area; a liquid
crystal layer; and a reflector layer; wherein the border area of
the CFG layer is fabricated to have a reflectivity that is
substantially the same as the active area.
14. The computing device of claim 13, wherein a given active pixel
in the active area of the CFG layer includes a transmissive hole
for transmitting color via a backlight; and wherein a given border
pixel in the border area of the CFG layer includes a black mask
area whose size and location within the given border pixel are
substantially the same as those of the transmissive hole for a
pixel in the active area.
15. The computing device of claim 14, wherein the size and location
of the black mask area within the given border pixel is adjusted to
match the reflectivity of a pixel in the active area when the
display is turned off.
16. The computing device of claim 13, wherein a given pixel in the
CFG layer includes a clear hole that allows ambient light to
reflect directly off of the reflector layer; wherein the clear hole
can be adjusted in size to tune the color point of the given pixel;
and wherein the size of a clear hole in the border area varies from
the size of a clear hole in the active area in order to adjust the
reflectivity of the border area to be substantially the same as in
the active area when the display is turned off.
17. The computing device of claim 13, wherein the pixel size in the
border area is different from the pixel size in the active area;
and wherein varying the pixel size can adjust the pixel's light
aperture ratio and can thereby change the pixels reflectivity.
18. The computing device of claim 17, wherein the size of pixels in
the border area can vary.
19. The computing device of claim 13, wherein the cell gap is the
distance between the CFG layer and the reflector layer; and wherein
the cell gap in the border area varies from the cell gap in the
active area; and wherein changing the cell gap in the border area
changes the reflectivity of the border area.
20. The computing device of claim 13, wherein the surface roughness
of the reflector layer in the border area varies from the surface
roughness of the reflector layer in the active area in order to
modify the reflectivity of the border area.
Description
BACKGROUND
1. Field of the Invention
The present invention generally relates to transflective liquid
crystal displays. More specifically, the present invention relates
to a reflective border area in a transflective display which is
cosmetically similar to an active area of the display when the
display is turned off.
2. Related Art
Explosive growth in the popularity of mobile communication and
computing devices has created a burgeoning demand for low-power
displays. Recently-developed transflective color displays provide
the ability to display information in a low-power, reflective mode
as well as through a transmissive mode which uses a backlight.
Transflective displays offer a compromise between purely
transmissive or reflective displays, since they can function
reflectively in bright sunlight, but can also be backlit when
needed in low-light conditions.
Unfortunately, existing transflective color displays suffer from a
cosmetic problem in some situations. Transflective color displays
typically have a black mask bordering the active pixels. However,
in a white transflective display, the active pixels are white when
the display is turned off. This results in a cosmetically
undesirable combination of a white active area bordered by the
black mask, with the black mask in turn bordered by the color of
the housing. Thus, when the display is turned off it has a
non-uniform appearance that is cosmetically undesirable.
Hence, what is needed is an apparatus and a method for alleviating
the above-described cosmetic problem with transflective
displays.
SUMMARY
One embodiment of the present invention provides a transflective
display in which a border area adjacent to an active area has a
reflectivity that is substantially the same as the active area when
the display is turned off. This display includes a polarizer layer,
a color filter glass (CFG) layer, a liquid crystal layer, and a
reflector layer. The CFG layer contains color filters in the active
area, while the border area of the CFG layer is designed to have a
reflectivity that is substantially the same as the active area when
the display is turned off.
In a variation on this embodiment, a given pixel in the active area
of the CFG layer includes a transmissive hole through which light
from a backlight is transmitted. Instead of a transmissive hole, a
given pixel in the border area of the CFG layer includes a black
mask region whose size and location
within the pixel are substantially the same as for the transmissive
hole for a pixel in the active area.
In a further variation on this embodiment, the size and location of
the black mask areas within pixels in the border area are adjusted
to match the reflectivity of pixels in the active area when the
display is turned off.
In a variation on this embodiment, a given pixel in the CFG layer
additionally includes a clear hole that allows ambient light to
reflect more directly off of the reflector layer and can be
adjusted in size to tune the color point of the pixel. The size of
the clear hole in the border area can differ from the size of the
clear hole in the active area to adjust the reflectivity of the
border area to be substantially the same as for the active
area.
In a variation on this embodiment, the pixel size in the border
area is different from the pixel size in the active area. Note that
varying a pixel's size can adjust the pixel's light aperture ratio,
and can thereby change the pixel's reflectivity.
In a further variation on this embodiment, the size of pixels in
the border area can vary.
In a variation on this embodiment, the distance between the CFG
layer and the reflector layer, known as the cell gap, can vary
between the border area and the active area, wherein changing the
cell gap in the border area changes the reflectivity of the border
area.
In a variation on this embodiment, the surface roughness of the
reflector layer in the border area varies from the surface
roughness of the reflector layer in the active area, thereby
modifying the reflectivity of the border area.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 illustrates a device with a transflective display in
accordance with an embodiment of the present invention.
FIG. 2 illustrates a cross-sectional view of the components of a
transflective color display in accordance with an embodiment of the
present invention.
FIG. 3 illustrates a frontal view of border pixels with black masks
in contrast to active area pixels with transmissive areas in
accordance with an embodiment of the present invention.
FIG. 4 illustrates border pixels having different sizes in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
The following description is presented to enable any person skilled
in the art to make and use the invention, and is provided in the
context of a particular application and its requirements. Various
modifications to the disclosed embodiments will be readily apparent
to those skilled in the art, and the general principles defined
herein may be applied to other embodiments and applications without
departing from the spirit and scope of the present invention. Thus,
the present invention is not limited to the embodiments shown, but
is to be accorded the widest scope consistent with the principles
and features disclosed herein.
Transflective Displays
In an ideal manufacturing process, the device housing precisely
borders the edge of a display's active area on all sides. However,
since such precision is beyond achievable tolerances of existing
cost-effective manufacturing technologies, transflective displays
typically include a visible border region between the active area
of the display and the device housing. This border region can
compensate for some amount of misalignment between the display and
the housing. A `border` is used to denote any area immediately or
mediately adjacent to the active area of a display. It need not
completely encircle the active area.
For example, FIG. 1 illustrates a device 100 with a transflective
display 102. The transflective display 102 includes an active area
104 and a border area 106. The border area 106 does not include
addressable pixels nor backlighting capabilities, and has different
reflective properties than the active area. The difference in
reflectivity, due in part to the presence of a black mask in the
border area, results in a darker color that gives the appearance of
a black line between the active area 104 and the device housing
108. Note that the border area can be larger, smaller, or more
irregular than shown in FIG. 1.
A common practice in display design is to copy the features of
either the reflective or the transmissive portions of the active
area into the border area. However, because the active and
non-active areas have different optical properties, this approach
still results in differing reflectivities in the different regions.
The present invention minimizes the visibility of the border area
when the device is powered off by minimizing the optical difference
between the active and border areas in transflective displays.
FIG. 2 illustrates a cross-sectional view of the components of a
transflective color display. More specifically, FIG. 2 illustrates
a portion of the display's border area 204 and active area 206, as
well as a portion of the area covered by the device housing 202.
The transflective display is composed of layers of material that
include: a polarizer 210; a layer of color filter glass (CFG) 212
coated with a combination of a black mask and red, green, and blue
color filters 214; a layer of liquid crystal 216 bordered by an
edge seal 218, that has a width specified by the cell gap 220; a
reflector layer 222 that is opaque in the border area but has
transmissive holes in the active area that allow light from the
backlight 232 to pass through; a circuitry layer 224 that includes
gate lines and edge circuits 226 in the border area and pixel
circuits 228 in the active area; a layer of thin-film transistor
(TFT) glass 230; and a backlight 232 that spans the active area and
may overlap into the border area.
Transflective color displays offer the ability to convey
information in both a reflective mode as well as via a transmissive
mode that operates by using the backlight 232. Note that no
information is conveyed in the non-addressable pixels of the border
area. In transmissive mode 240, light from the backlight 232 shines
through the holes in the reflector layer, and is modified by the
liquid crystal layer 216, which is controlled by the pixel circuits
228. The modified light then passes through a transmissive area 242
in the color filters (212-214) and through the polarizer 210. The
system converts the white backlight into specific colors by
controlling the intensity of light that passes through the liquid
crystal display and which is directed into the red, green, and blue
filters of the transmissive area.
In reflective mode 244, ambient light passes through the polarizer
and color filter layers (210-214) and is modified in intensity by
the liquid crystal layer 216. The modified light then reflects off
of the reflector layer 222 to exit through the display by passing
back through the above-mentioned layers a second time. The
reflected light enters through the reflective area 246 in the color
filters (212-214), which is distinct and offset from the
transmissive area 242.
While both the reflective and transmissive areas are present in the
active area of the display, within the border area the transmissive
areas are instead replaced by a black mask 248. Note that the
reflective areas are present in both the active and border areas,
but are only actually used to convey information in the active
area.
Matching Reflectivity in Transflective Displays
FIG. 3 illustrates a frontal view of border pixels that contain a
color filter and reflector pattern that are substantially the same
as that of the active area, with a black mask 248 placed in the
transmissive areas. Within a given border pixel 302, a black mask
area 248 whose size and location within the pixel are substantially
the same as those of a corresponding transmissive area in a pixel
of the active area 304 reduces the reflectivity of the border
pixel. Since the black mask often reflects less light than a
transmissive area of substantially the same size, due to some
limited amount of reflectivity from the backlight in the
transmissive area, the size of the black mask is typically adjusted
(reduced) to match the reflectivity of the transmissive area. Thus,
the size and location of the black mask areas in pixels of the
border region can be tuned to increase or decrease the reflectivity
of the border area as desired.
In reflective mode, some amount of light is lost as the ambient
light passes through the layers of the screen, reflects against the
reflector layer, and then passed out through the screen again. Less
light is lost in transmissive mode, since the light only passes
through the screen once. An additional area can be provided in each
sub-pixel to improve the brightness of the display in reflective
mode. For example, "clear holes" 306 in each sub-pixel contain no
filters or masks, and allow ambient light to pass through and
reflect unimpeded from the reflector layer. These clear holes,
which may be of different size for each type (red, green, or blue)
of sub-pixel, provide an adjustment mechanism that allows the color
purity of the reflective mode to match the color purity of the
transmissive mode more closely. As a secondary effect, the use of
clear holes also results in additional reflection through the color
filters as well.
In general, clear holes improve reflectivity, resulting in a
brighter display and white point, higher contrast, and better color
mixing. Furthermore, the size and location of the clear holes
within each given pixel of the border area can additionally be
modified to further match the reflectivity of pixels in the border
area with pixels of the active area.
The size of pixels in the border area can also be used to adjust
the reflectivity of the region. For example, FIG. 4 illustrates
edge pixels whose sizes are modified 402 to fit the display area.
Resizing options include scaling the edge pixels to fit, as shown
in FIG. 4, or uniformly resizing the border pixels so that a
discrete number of same-size pixels fill the border region. Since
changing the size of a pixel changes the size and pitch of the
reflective area, clear holes, and black mask, and thus changes the
aperture ratio of the pixel, this technique provides an additional
mechanism for changing the reflectivity of the border region to
match the active area.
A further set of mechanisms for adjusting the reflectivity of the
border area involves modifying the cell gap and the surface
roughness of the reflector layer in the border area. For the former
case, the cell gap, or the distance between the CFG layer and the
reflector layer, can be varied in the border area from the cell gap
in the active area.
The foregoing descriptions of embodiments of the present invention
have been presented only for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
present invention to the forms disclosed. Accordingly, many
modifications and variations will be apparent to practitioners
skilled in the art. Additionally, the above disclosure is not
intended to limit the present invention. The scope of the present
invention is defined by the appended claims.
* * * * *